Integrated Organic Farming Improves the Carbon Balance: Observations From Glenlea, Canada.

Sustainability of agriculture is very much a function of how the farming system deals with carbon.  Fossil fuel use, human usable crop and livestock energy and soil carbon storage were measured in a long-term field experiment in Manitoba, Canada.  Since 1992, the Glenlea long-term study compares two farming systems (grain only vs forage-grain) under organic and conventional management.  Fossil fuel energy use in the grain only and forage-grain systems averaged 2019 and 1848 MJ/ha/year, respectively under organic management and 5708 and 4104 MJ/ha/year, respectively under conventional management.  Therefore, organic production used 55 to 65% less energy than conventional production.  Human usable food energy production was 46% lower under organic than conventional management in the grain only system but only 15% lower in the forage-grain system.   Energy use efficiency was greatest in the organic forage-grain system; 42% higher than the conventional grain only system.  After 13 years (2004), soil organic carbon was significantly lower in the grain only system, regardless of management system.  Therefore, compared with the standard farming system in the region (conventional grain production) the forage-grain rotation under organic management required 65% less input energy; produced 85% as much human usable energy; and resulted in 11% more surface soil organic carbon.